| 摘要 |
An <<eye-piece>> system for an infra-red afocal telescope comprises a back element (17) of positive power having a convex front surface and a curved back surface, and a pair of elements (15, 16) closely spaced to define a gas lens therebetween, the front element (15) of the pair having a concave front surface whose radius of curvature is equal to or greater than that of the convex back surface of the back element (16) of the pair, the pair of elements in combination with the gas lens therebetween being of positive power. The <<eye-piece>> system can be used in combination with an objective lens system, which may be catadioptric (11, 12, 13, 14) or all refractive, to provide a collimated magnified view of a scene or object, from which infra-red radiation is received, at a real exit pupil where a scanner (18) operates.
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